House Mice in the Atlantic Region: Genetic Signals of Their Human Transport

Abstract

Background/objectives: The colonization history of house mice reflects the maritime history of humans that passively transported them worldwide. We investigated western house mouse colonization in the Atlantic region through studies of mitochondrial D-loop DNA sequences from modern specimens.

Methods: We assembled a dataset of 758 haplotypes derived from 2765 mice from 47 countries/oceanic archipelagos (a combination of new and published data). Our maximum likelihood phylogeny recovered five previously identified clades, and we used the haplotype affinities within the phylogeny to infer house mouse colonization history, employing statistical tests and indices. From human history, we predefined four European source areas for mice in the Atlantic region (Northern Europe excluding Scandinavia, Southern Europe, Scandinavia, and Macaronesia) and we investigated the colonization from these source areas to different geographic areas in the Atlantic region.

Results: Our inferences suggest mouse colonization of Scandinavia itself from Northern Europe, and Macaronesia from both Southern Europe and Scandinavia/Germany (the latter likely representing the transport of mice by Vikings). Mice on North Atlantic islands apparently derive primarily from Scandinavia, while for South Atlantic islands, North America, and Sub-Saharan Africa, the clearest source is Northern Europe, although mice on South Atlantic islands also had genetic inputs from Macaronesia and Southern Europe (for Tristan da Cunha). Macaronesia was a stopover for Atlantic voyages, creating an opportunity for mouse infestation. Mice in Latin America also apparently had multiple colonization sources, with a strong Southern European signal but also input from Northern Europe and/or Macaronesia.

Conclusions: D-loop sequences help discern the broad-scale colonization history of house mice and new perspectives on human history.

Keywords: Age of Discovery; D-loop; Mus musculus domesticus; Vikings; colonization history; phylogeography.

Figure 1

Summary phylogenetic tree for all house mouse haplotypes under consideration, highlighting the particular source areas for Atlantic colonization associated with each of the five previously named clades (B–F) found in the region. The outgroups and the haplotypes that could not be attributed with confidence to a previously named clade had their branches colored black. The naming of the geographic areas follows the convention in this paper. See Figures S1 and S2 for the full tree (including branch support) and further explanation. The phylogeny is based on our new sequences (Table S1) and previously published sequences (Text S2). Particular sequences of importance for interpretation (see Section 3.2 below) are presented in Table S3 (with subsidiary information in Table S2).

Figure 2

Inferred colonization history of house mice in the Atlantic region from the four defined source areas (Northern Europe, Southern Europe, Scandinavia, Macaronesia) to the five defined colonized areas (North Atlantic, North America, Latin America, South Atlantic, Sub-Saharan Africa). Solid arrows indicate the main routes of colonization. For Latin America, there is a major signal of mouse colonization from Southern Europe but also data suggesting at least partial derivation from Macaronesia and/or Northern Europe (shown with dashed arrows). For the South Atlantic islands, the clade analysis indicates the pre-eminence of Northern Europe in mouse colonization, but multi-location haplotypes support the involvement of Macaronesia and Southern Europe as well (dotted arrows). The most indicative clades present in the source and colonized areas for each of these linkages are shown within circles. There are insufficient data to infer the colonization history of the Caribbean by house mice. The coloring used here does not relate to the coloring in the phylogenetic trees. AP: Azores, CV: Cabo Verde, FK: Falkland (Malvinas) Islands, FO: Faroe, GL: Greenland, GP: Guadeloupe, GS: South Georgia, IC: Canary Islands, IS: Iceland, MQ: Martinique, TA: Tristan da Cunha, XG: Gough Island, XM: Madeira, XP: Marion Island.